The invention relates to a curable composition, methods for applying the composition as well as end-uses for the cured composition
Sealants are employed in a wide range of applications. For example, the automotive industry employs sealants between and upon metal seams and welds, within hollow cavities to impart structural and sound damping characteristics, among other locations.
One specific sealant environment involves the use of a sealant upon the welds in the so-called xe2x80x9croof-ditchxe2x80x9d which is formed when joining the side panels of the body to the roof of the vehicle. The roof-ditch weld is conventionally covered with a bead or strip of polyvinyl chloride (PVC) based molding that is typically covered with a metal strip and painted. The PVC strip typically contains plasticizers, stabilizers, lubricants, among other compounds that can volatilize from the strip thereby causing cracking and shrinking. When the PVC strip cracks such can reduce the effectiveness of the strip and in turn allow the underlying metal to corrode.
Conventional sealants including those employed in roof ditches can also create conditions which are conducive to microbial, e.g., fungal, growth; especially in warm humid environments. The microbe growth occurs because the sealant contains substances that can be metabolized by the microbe. Consequently, there is a need in the sealant industry for a sealant with enhanced durability, and microbial resistance and cosmetic value that can be applied in an expedient manner. There is also a need in this industry for a sealant that can be repaired or replaced.
Methods for applying and curing/heating coatings are described in U.S. Pat. No. 4,844,947 (Kasner et al.), U.S. Pat. No. 5,348,604 (Neff) and U.S. Pat. No. 5,453,451 (Sokol). The disclosure of the previously identified patents is hereby incorporated by reference in their entirety for all purposes.
This invention is capable of solving problems associated with conventional practices by providing a radiation curable composition, which can be employed as a sealant that is easy to manipulate, durable, paintable, repairable/replaceable, crack and microbe resistant, e.g., mildew.
The inventive composition can be employed in a wide range of environments including in the automotive industry, e.g., as a roof-ditch sealant. The composition of the invention can be applied by using commercially available dispensing equipment, e.g., brushing, dipping, spraying or pumping, and cured in-situ, e.g., by a source of energy or radiation such as UV radiation, electron beam, laser, microwave, among other energy sources sufficient to cause curing sufficient to control sag or material flow for a specific application. If desired, the inventive composition can be painted.
In one aspect, the curable composition according to this invention comprises at least one epoxy compound, at least one carrier, e.g., polyol, and at least one suitable photoinitiators. In addition, the curable composition can optionally include at least one thickener or filler, as well as at least one monomers and/or at least one phenoxy resins. In one embodiment, the inventive composition can comprise: 1) at least one epoxy such as that supplied by UCB Radcure as Uvacure 1500, 1530, and 1534 or by Sartomer as SARCAT K126, 2) at least one and preferably two or more polyols such as the polyester polyols supplied by Union Carbide as Tone 0301 and by Huls America as Dynacoll 7110, 3) at least one photoinitiator such as sulfonium salt supplied by Union Carbide as Cyracure UVI 6974 and by Sartomer as CD1010; and optionally, the following additional three components, 4) at least one thickener or filler such as silicon dioxide supplied by Cabot Corporation and 5) at least one monomer such as TONE M-100 also supplied by Union Carbide, a hydroxy polyester acrylate/hydroxyethyl acrylate blend or a monomer such as caprolactone acrylate supplied by Sartomer; and 6) at least one phenoxy resin such as phenoxy resin such as phenoxy resin PKHP 200 supplied by Phenoxy Specialties.
In another aspect, the curable composition is pre-initiated before contacting the substrate. By xe2x80x9cpre-initiatedxe2x80x9d, xe2x80x9cpre-initiatingxe2x80x9d or xe2x80x9cpre-initiate(s)xe2x80x9d it is meant exposure to a suitable source of energy or radiation at least once: 1) while combining the components of the composition, 2) when preparing at least one component of the composition prior to combining with other components, 3) during transport of the composition or components thereof through a conduit or related handling equipment, among other suitable techniques to pre-initiate curing of the composition. If desired, the composition can be pre-initiated by a radiation source that is embedded or located within or upon a conduit or other member such that radiation can be supplied to the composition or components thereof, e.g, UV radiation is shown through a window on a conduit that delivers the composition to a substrate. The radiation source may also be embedded within the system for dispensing the composition, e.g., a UV source located within a nozzle that applies the composition onto a substrate. Pre-initiating the curable composition permits controlling the viscosity of the composition as well as reducing the curing time after being applied onto a substrate.
These and other aspects of the invention will become apparent from the specification and claims which follows.